<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
		<title>Document</title>
	</head>

	<body>
		<button>点击</button>
		<script>
			const btn = document.querySelector("button");
			function fn() {
				console.log("我是回调函数A");
			}

			function fn2() {
				console.log("我是回调函数B");
			}
			btn.addEventListener("click", fn);
			btn.addEventListener("click", fn2);

			// 消除这个事件fn2
			btn.removeEventListener("click", fn2);
		</script>
	</body>
</html>
